#include<stdlib.h>

struct ListNode 
{
      int val;
      struct ListNode *next;
};
 

int main()
{
    struct ListNode* n1 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n2 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n3 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n4 = (struct ListNode*)malloc(sizeof(struct ListNode));
    n1->val = 1;
    n2->val = 2;
    n3->val = 3;
    n4->val = 4;

    n1->next = n2;
    n2->next = n3;
    n3->next = n4;
    n4->next = NULL;
}


struct ListNode* removeElements(struct ListNode* head, int val)
{
    struct ListNode* cur = head;
    struct ListNode* prev = NULL;
    while (cur != NULL)
    {
        if (cur->val != val)
        {
            prev = cur;
            cur = cur->next;
        }
        else
        {

            if (prev == NULL)
            {
                head = cur->next;
                free(cur);
                cur = head;

            }
            else
            {
                prev->next = cur->next;
                free(cur);
                cur = prev->next;
            }
        }
    }
    return head;
}